Regioselective Oxidative Ring Cleavage of a Phlorin Analogue: An Approach for Synthesizing Linear Tetrapyrroles

Abstract

Oxidation of neo-N-confused phlorin 1 with excessive FeCl leads to regioselective ring opening, generating three linear tetrapyrroles, i.e., (10 Z,15 Z)-biladienone 2, (10 Z,15 E)-biladienone 3, and 19-methoxy (10 Z,15 E)-biladiene 4 with an overall yield of 88%. The coordination of these compounds with Zn(II) is affected by the inverted terminal pyrrolic unit, and the presence of the electron-withdrawing keto moiety. The structural identities were also clearly elucidated by the crystal structures of 3 and 4-Zn and were rationalized by DFT calculations.

Loading Phlorins with Fullerenes by a [4 + 2]-Cycloaddition Reaction: Regulation of the Regioselectivity by Pyrrole Linkage Modes

“… − These new species feature excellent long-wavelength absorption, enriched redox activities, and outstanding affinity toward anion (e.g., F – , AcO – ). , Although the synthesis of phlorin can date back to 1960 when Woodward employed it as an intermediate in the total synthesis of chlorophyll, the breakthrough for efficiently preparing such macrocycles took place until early 2000. Thereafter, many novel phlorin derivatives such as N-confused phlorins, − core-modified phlorins, − and expanded phlorins − have been prepared with the aim to investigate the chemical transformations, unique photophysical properties, as well as chelating/sensing behaviors in-depth. However, the restriction of the meso-substituents (C 6 F 5, etc.)…”